Metal additive manufacturing equipment

Abstract

To provide a metal laminate molding apparatus that can improve the shape accuracy in a first area portion where there is no sustainment due to nonexistence of a molding portion solidified by an optical beam in a lower part in a lamination direction.SOLUTION: A metal laminate molding apparatus for laminate molding a structure by a repetition of irradiating a powder layer which is a layer of metal powder, with an optical beam and laminating it through melting and solidification, wherein the structure has a first area portion where no molding portion solidified by the optical beam exists in a lower part in a lamination direction, and a second area portion where the molding portion exists in the lower part, comprises a storage portion that previously stores identification information for identifying the first area portion and the second area portion, and a condition adjusting portion that adjusts a molding condition for determining an energy density so as to input heat with a lower energy density during molding the first area portion than during molding the second area portion based on the identification information.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a metal additive manufacturing apparatus.

Background Art

[0002] Conventionally, as described in, for example, Patent Document 1, there is known a metal additive manufacturing apparatus that repeatedly irradiates a layer of metal powder with a light beam such as a laser, melts and solidifies it, and stacks it to form a structure. As the metal powder, various metals such as aluminum, titanium, nickel, stainless steel, and copper alloys are used. Such a metal additive manufacturing apparatus is expected in various fields from mechanical parts to electrical parts because it enables fine shaping.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when forming a structure such as a water pipe in which an axially extending cavity used as a flow path or the like is formed, by additive manufacturing from below to above in a cross section in a plane perpendicular to the axial direction, there is a risk of a large shape error occurring in the upper half of the structure in the direction of gravity. Specifically, in a cross section in a plane perpendicular to the axial direction of the flow path, the lower half in the direction of gravity of the portion forming the inner peripheral surface can be accurately shaped because there is a shaping portion that serves as a support during shaping. However, the upper half in the direction of gravity of the portion forming the inner peripheral surface does not have a support directly below because the already shaped (solidified) portion does not exist directly below during shaping, resulting in a state of excessive heat input compared to the portion with a support, causing a shape error and deterioration of shape accuracy.

Means for Solving the Problems

[0005] This disclosure can be implemented in the following forms: According to one embodiment of the present disclosure, a metal additive manufacturing apparatus is provided that repeatedly irradiates a powder layer, which is a layer of metal powder, with a light beam to melt and solidify it, thereby additively manufacturing a structure. The structure has a first area where the solidified part by the light beam is not located at the bottom in the stacking direction, and a second area where the solidified part is located at the bottom. The metal additive manufacturing apparatus includes a storage unit that stores identification information for distinguishing between the first area and the second area, and a condition adjustment unit that adjusts the manufacturing conditions for determining the energy density based on the identification information, such that when manufacturing the first area, the heat input is lower than when manufacturing the second area. The storage unit stores the first area at the same energy density as the second area. The identification information further stores information that identifies a generating area where warping exceeding a predetermined shape error occurs when fabricated, and a non-generating area where warping does not occur when fabricated with the same energy density as the second area. The condition adjustment unit adjusts the fabrication conditions to be different from the beam output when fabricating the generating area, such that the beam output, which is the output of the light beam, is the same as the beam output when fabricating the non-generating area, and the beam irradiation temperature in the generating area is the same as the beam irradiation temperature in the non-generating area.

[0006] (1) According to one embodiment of the present disclosure, a metal additive manufacturing apparatus is provided. This metal additive manufacturing apparatus is a metal additive manufacturing apparatus that additively manufactures a structure by repeatedly irradiating a powder layer, which is a layer of metal powder, with a light beam to melt and solidify it, and then stacking the structures, wherein the structure has a first area where the solidified part by the light beam is not located at the bottom in the stacking direction, and a second area where the solidified part is located at the bottom, and comprises a storage unit that stores identification information for distinguishing between the first area and the second area, and a condition adjustment unit that adjusts the manufacturing conditions for determining the energy density based on the identification information so that when manufacturing the first area, the heat input is lower than when manufacturing the second area. When creating a first area where the solidified part formed by the light beam is not located at the bottom in the layering direction and there is no support underneath, if the light beam is irradiated with the same energy density as the second area where a supporting part is located below, it can result in excessive heat input compared to the second area, making it prone to shape errors and potentially degrading shape accuracy. In the metal additive manufacturing apparatus of the above configuration, identification information that distinguishes between the first and second areas is stored in the memory unit. Based on this identification information, the condition adjustment unit can adjust the manufacturing conditions to determine the energy density so that the heat input during the creation of the first area is lower than that during the creation of the second area. As a result, excessive heat input in the first area can be suppressed, and shape accuracy can be improved. (2) In the above embodiment, the memory unit further stores as identification information information which identifies which of the first area is a generating area in which warping exceeding a predetermined shape error occurs when fabricated with the same energy density as the second area, and which is a non-generating area in which warping does not occur when fabricated with the same energy density as the second area. The condition adjustment unit may adjust the fabrication conditions to be different from the beam output when fabricating the generating area, such that the beam output, which is the output of the light beam, is the same as the beam output when fabricating the non-generating area, and the beam irradiation temperature in the generating area is the same as the beam irradiation temperature in the non-generating area. In this type of metal additive manufacturing apparatus, for areas in the first area where warping exceeding a predetermined shape error occurs when manufactured under the same manufacturing conditions as the second area, the condition adjustment unit can adjust the heat input to a lower energy density than during manufacturing in the second area. Areas where warping does not occur do not require energy density adjustment, even at the same energy density as during manufacturing in the second area. In the above embodiment, since the energy density is adjusted to be lower for areas where warping exceeding a shape error that deteriorates shape accuracy occurs, it is a suitable embodiment for making adjustments to the necessary parts. (3) In the above embodiment, the metal powder may be a copper alloy. Copper alloy powder has a high reflectivity and does not easily absorb the energy of the light beam, making additive manufacturing relatively difficult. Even with such copper alloy powder, the metal additive manufacturing apparatus of the above embodiment can improve the shape accuracy of the fabricated structure. (4) In the above embodiment, the structure may have a pipeline through which a fluid flows, and the first area may be formed on the curved inner circumference that forms the pipeline. With this embodiment of the metal additive manufacturing apparatus, the shape accuracy of the first area formed on the curved inner circumference of the structure having a pipeline can be improved. (5) In the above embodiment, the structure may be a coil for high-frequency heat treatment. With this embodiment of the metal additive manufacturing apparatus, a coil for high-frequency heat treatment can be manufactured by additive manufacturing with good shape accuracy. (6) In the above embodiment, the condition adjustment unit may adjust at least one of the following conditions as the molding conditions: the scanning speed of the light beam, the scanning pitch of the light beam, and the layer thickness of the powder layer. According to this embodiment of the metal additive manufacturing apparatus, the energy density can be adjusted using at least one of the following conditions: the scanning speed of the light beam, the scanning pitch of the light beam, and the layer thickness of the powder layer. [Brief explanation of the drawing]

[0007] [Figure 1] This is a cross-sectional view showing the schematic configuration of a metal additive manufacturing apparatus in a first embodiment of the present disclosure. [Figure 2] This is a schematic diagram illustrating beam irradiation using a beam irradiation device. [Figure 3] This is a schematic block diagram showing the functional configuration of a metal additive manufacturing system. [Figure 4] This is a cross-sectional view showing a structure fabricated by a metal additive manufacturing machine. [Figure 5] This is a schematic diagram illustrating the theoretical formula for energy density during beam irradiation. [Figure 6] This figure shows the relationship between energy density and beam irradiation temperature. [Figure 7] This figure shows the relationship between energy density and fabrication conditions. [Figure 8] Figure 7 is a close-up cross-sectional photograph showing a portion of the structure that was fabricated after the adjustments made to the conditions shown. [Figure 9] This figure shows the relationship between energy density and fabrication conditions. [Figure 10] Figure 9 is a cross-sectional photograph showing a magnified view of a portion of the structure that was fabricated after the adjustments made to the conditions shown. [Figure 11] This diagram illustrates the occurrence of shape errors when fabricating pipes with varying radius using a comparative metal additive manufacturing apparatus. [Figure 12] This is a diagram for explaining the occurrence of shape errors when forming by changing the radius of a pipeline using the metal additive manufacturing apparatus of the first embodiment.

Mode for Carrying Out the Invention

[0008] A. First Embodiment: A1. Overall Configuration of Metal Additive Manufacturing Apparatus 1: FIG. 1 is a cross-sectional view showing the schematic configuration of a metal additive manufacturing apparatus 1 according to the first embodiment of the present disclosure. The metal additive manufacturing apparatus 1 forms a three-dimensional structure W by additive manufacturing using the powder bed method. Specifically, the metal additive manufacturing apparatus 1 irradiates a laser beam onto a powder layer PL, which is a layer of metal powder M, to melt and solidify it, then covers the upper layer with the metal powder M again to form the powder layer PL, and repeats the operation of irradiating a laser beam thereon to stack and form the structure W.

[0009] In the first embodiment, a laser beam is used as the light beam. Note that the light beam includes, in addition to the laser beam, an electron beam and various other beams that can melt the metal powder M. Also, various lasers such as a near-infrared wavelength laser, a CO2 laser (far-infrared laser), and a semiconductor laser can be applied to the laser beam, and it is appropriately determined according to the target metal powder M. In the first embodiment, the metal powder M is a copper alloy. Note that, as the metal powder M, in addition to the copper alloy, various metal materials such as aluminum, pure copper, steel materials such as maraging steel and inconel, and stainless steel can be applied.

[0010] As shown in FIG. 1, the metal additive manufacturing apparatus 1 includes a chamber 10, a structure support device 20, a powder supply device 30, and a beam irradiation device 40. The chamber 10 is configured to be able to replace the internal air with an inert gas such as He (helium), N2 (nitrogen), or Ar (argon). Note that the chamber 10 may be configured to be depressurized instead of replacing the inside with an inert gas.

[0011] The shaped object support device 20 is provided inside the chamber 10 and is a part for shaping the structure W. The shaped object support device 20 includes a shaping container 21, a lifting table 22, and a base 23. The shaping container 21 has an opening at the upper side and has an inner wall surface parallel to the vertical axis. The lifting table 22 is provided inside the shaping container 21 so as to be movable vertically along the inner wall surface. The base 23 is detachably attached to the upper surface of the lifting table 22, and the upper surface of the base 23 becomes a part for shaping the structure W. That is, the base 23 arranges the metal powder M in layers on the upper surface and supports the structure W during shaping. By changing the positioning height of the lifting table 22, the stacking thickness of the metal powder M can be changed.

[0012] The powder supply device 30 is provided inside the chamber 10 adjacent to the shaped object support device 20. The powder supply device 30 includes a powder storage container 31, a supply table 32, and a recoater 33. The powder storage container 31 has an opening at the upper side, and the height of the opening of the powder storage container 31 is provided to be the same as the height of the opening of the shaping container 21. The powder storage container 31 has an inner wall surface parallel to the vertical axis. The supply table 32 is provided inside the powder storage container 31 so as to be movable vertically along the inner wall surface. And inside the powder storage container 31, the metal powder M is stored in the upper region of the supply table 32.

[0013] The recoater 33 is provided so as to be reciprocally movable along the upper surfaces of both openings across the entire regions of the opening of the shaping container 21 and the opening of the powder storage container 31. When the recoater 33 moves from right to left in FIG. 1, it transports the metal powder M protruding from the opening of the powder storage container 31 to the shaping container 21 side. Further, the recoater 33 arranges the transported metal powder M in layers on the upper surface of the base 23. In addition to the above configuration, it is also possible to make the movable recoater 33 itself have a function of supplying the metal powder M. In this case, the metal powder M is flattened while being supplied onto the base 23 by the recoater 33.

[0014] Figure 2 is a schematic diagram illustrating beam irradiation by the beam irradiation device 40. As shown in Figure 2, the beam irradiation device 40 irradiates the surface of the powder layer PL, which is a layer of metal powder M arranged in layers on the upper surface of the base 23, with a beam. By irradiating the layered metal powder M with a beam, the beam irradiation device 40 heats the metal powder M to a temperature above its melting point. As a result, the metal powder M melts and then solidifies, forming integrated layered structures W11, W12, and W13 (all parts of the structure W). In other words, adjacent metal powders M are integrated by fusion joining.

[0015] Figure 3 is a schematic block diagram showing the functional configuration of the metal additive manufacturing apparatus 1. As shown in Figure 3, the metal additive manufacturing apparatus 1 is equipped with a control device 50. The control device 50 includes a storage unit 51 and a condition adjustment unit 52. The storage unit 51 stores various information related to the structure W. Specifically, for example, it stores information on the two-dimensional cross-sectional shape to be layered, based on the three-dimensional data of the structure W, using slicer software or the like.

[0016] The control device 50 is, for example, a microcomputer including a CPU, ROM, RAM, and other input / output ports, and controls the entire metal additive manufacturing apparatus 11. The CPU of this microcomputer functions as the condition adjustment unit 52 by reading and executing a program stored in the ROM.

[0017] Figure 4 is a cross-sectional view showing a structure W1 fabricated by a metal additive manufacturing apparatus 1. In the first embodiment, the structure W1 fabricated is a coil for high-frequency heat treatment. The structure W1 has a conduit 60 through which water flows as a fluid. Figure 4 shows a cross-section (hereinafter simply referred to as the "axial cross-section") cut by a plane perpendicular to the axial direction in which the conduit 60 extends. The right side of Figure 4 shows an enlarged view of the area around the conduit 60 on the left side of Figure 4. The axial cross-sectional shape of the conduit 60 is approximately semicircular. The radius R of the conduit 60 is 8 mm. The axial cross-sectional shape of the conduit 60 is not limited to approximately semicircular, but can be a perfect circle, an ellipse, a polygon such as a triangle or quadrilateral, or a shape formed by any straight line and curve.

[0018] The structure W1 has a first area 61 and a second area 62. The first area 61 is a part of the structure W1 in which the solidified part formed by the light beam is not located at the bottom in the stacking direction Z. Specifically, the first area 61 is formed on the outside of the conduit 60 and on the inner circumference which is curved. The second area 62 is a part of the structure W1 in which the solidified part formed by the light beam is located at the bottom. Specifically, the second area 62 is located on the outside of the straight section and the inner circumference which are at the bottom of the outside of the conduit 60 and on the outside of the inner circumference which is a part in which the solidified part is not located at the bottom in the stacking direction Z.

[0019] Figure 4 illustrates the shape when the energy density E, which will be described later, is not adjusted in the condition adjustment unit 52, and the entire first area 61 and second area 62 are fabricated under the same fabrication conditions. Therefore, shape distortion can be seen near the top surface 66, which is enclosed by a dashed line. The phrase "when the energy density E is not adjusted in the condition adjustment unit 52, and the entire first area 61 and second area 62 are fabricated under the same fabrication conditions" will also be referred to simply as "when no condition adjustment is performed" below.

[0020] The first area 61, fabricated without any adjustment of the conditions, is divided into a warping area 64 and a non-warping area 65. The warping area 64 is the part where warping exceeding a predetermined allowable shape error occurs when fabricated by irradiating it with a beam under the same fabrication conditions as the second area 62. The non-warping area 65 is the part where the above-mentioned warping does not occur when fabricated by irradiating it with a beam under the same fabrication conditions as the second area 62. "Warping exceeding the allowable shape error" refers to, for example, warping that exceeds the thickness of one layer. As shown in the enlarged view on the right side of Figure 4, of the first area 61, for example, 379 layers are layers with non-warping areas 65, and 399 layers are layers that partially have warping areas 64.

[0021] The storage unit 51 stores identification information to distinguish between the first area unit 61 and the second area unit 62. Furthermore, the storage unit 51 stores information to distinguish between the generation unit 64 and the non-generation unit 65 as identification information.

[0022] The above-mentioned condition adjustment unit 52 adjusts the various irradiation conditions and building conditions, including the layer thickness, of the beam irradiation device 40 based on the identification information. Specifically, the condition adjustment unit 52 adjusts the heat input during the building of the generation unit 64 so that it is lower in energy density E than the non-generation unit 65 and the second area unit 62. A detailed explanation of the condition adjustment using specific numerical data will be described later.

[0023] Figure 5 is a schematic diagram illustrating the theoretical formula for the energy density E during beam irradiation. The condition adjustment unit 52 changes the irradiation position, laser output P [W], scanning speed v [mm / s], scanning pitch s [mm], layer thickness t [mm], etc., according to a preset program. By changing the irradiation position, a desired layered structure can be fabricated. Furthermore, by changing the laser output P, ​​the amount of heat input into the metal powder M changes, and the bonding strength between the metal powders M can be changed. The energy density E, which correlates with the amount of heat input, can be adjusted by parameters based on the following theoretical formula (1). Energy density: E = P / (v × s × t) ... (1)

[0024] A2. Adjustment by the condition adjustment unit 52: Next, the condition adjustments performed by the condition adjustment unit 52 when fabricating the structure W1 using the metal additive manufacturing apparatus 1 will be explained using data. When fabricating in the generation unit 64, the condition adjustment unit 52 adjusts fabrication conditions other than the beam output so that the beam output is the same as the beam output when fabricating in the non-generation unit 65, and the beam irradiation temperature of the generation unit 64 is the same as the beam irradiation temperature of the non-generation unit 65.

[0025] Furthermore, the terms "identical" and "same" used here are not limited to "identical" and "same" in the strict sense, but are interpreted as "identical" and "same" if they possess a degree of identity that would ordinarily be considered "identical" and "same" in light of common technical knowledge in the relevant technical field. Specifically, differences of approximately 20% increase or decrease from the standard value may be included in the definition of "identical."

[0026] Figure 6 shows the correspondence between energy density E and beam irradiation temperature. Here, "beam irradiation temperature" refers to the average temperature around the laser irradiation point. The area around the laser irradiation point includes the molten pool N (see Figure 5) formed by the melting of metal powder M due to laser irradiation. In the data shown in Figure 6, the "irradiation temperature" was derived by plotting multiple points around the laser irradiation point and analyzing the data.

[0027] The configuration of the structure fabricated with the energy density E shown in cases 1 and 2 of Figure 6 matches the structure W1 shown in Figure 4. As shown in cases 1 and 2 of Figures 4 and 6, the energy density E is 231 J / mm². 3 In this case, no warping occurred in layer 379, but in layer 399, warping occurred near the top surface 66 in layer 399, resulting in deformation. Comparing the irradiation temperatures obtained from the above analysis, the irradiation temperature of the area 64 where warping occurred in layer 399 was 3700°C, while the irradiation temperature of the area 65 where warping did not occur in layer 379 was 1350°C.

[0028] In other words, the non-occurring area 65 (379 layers) had a significantly higher temperature during irradiation. As shown in Figure 4, the inventors' investigation revealed that even within the first area 61 without support, shape deformation occurred in areas closer to the top surface 66. Specifically, the areas closer to the top surface 66 are those where the tangent angle θ of the inner circumferential surface (the angle between the tangent and the horizontal plane passing through the point of contact, which is the counterclockwise angle in Figure 4) is in the range of 30 to 150 degrees. The areas with a tangent angle θ of around 90 degrees showed the largest shape error.

[0029] Here, we will briefly explain the principle behind shape deformation. As the fabrication progresses and layers are built up from the bottom to the vicinity of the top surface 66, the length L1 (see Figure 2) of the area where the laser is irradiated to the powder layer PL increases. In particular, in the powder layer PL near the top surface 66, when the laser is irradiated to the metal powder M, the length L2 of the area directly below the irradiated area where the metal powder M has not solidified is longer than the corresponding length L3 of the lower layer. In other words, the contact area with the area where the metal powder M has not solidified becomes larger. Unsolidified metal powder M has a lower thermal conductivity than solidified metal, and since the thickness of one powder layer PL is very thin at 40 μm, if the laser irradiation to the generation area 64 has the same energy density E as the laser irradiation to the non-generation area 65, it becomes difficult to dissipate heat to the lower layer, and heat accumulates.

[0030] As a result, the amount of heat input to the generation unit 64 increased, meaning that the thermal expansion was greater than that of the lower layer (for example, when creating the molding unit W13, the molding unit W12 below it as shown in Figure 2). Eventually, when the generation unit 64 cooled and contracted, the lower layer, which retained its shape, warped upwards. When warping occurred, it was impossible to spread the metal powder M evenly on top of it using the recoater 33. Alternatively, even if it was spread evenly, the thickness of one layer became partially thinner, and the excessive heat input led to a buildup of errors, ultimately causing the area around the top surface 66 to collapse downwards beyond the acceptable limit. This resulted in a deformation that exceeded the acceptable limit.

[0031] Therefore, the inventors of this application considered that if the irradiation temperature of the generating section 64 was lowered to be about the same as that of the non-generating section 65, excessive heat input could be suppressed and warping could be controlled. Refer again to Figure 6. Through the inventors' analysis, the energy density E of the generating section 64 (399 layers) was found to be 231 J / mm² as shown in case 2. 3 As shown in case 3, 85 J / mm 3 By reducing the size, the temperature could be lowered to 1400°C, which is equivalent to the temperature of 379 layers. Here, the energy density E can be calculated using equation (1) above. From equation (1), to lower the energy density E, it is possible to either lower the laser output P, ​​or increase the value of either the scanning speed v, scanning pitch s, or the layer thickness t.

[0032] The following study investigated which fabrication conditions are most suitable for lowering the energy density E. Figure 7 shows the correspondence between energy density E and fabrication conditions, and the scanning speed v is used as the adjustment condition. The data shows the results when the energy density E is reduced by increasing the scanning speed v. In the example shown in Figure 7, the scanning speed v is changed from 500 mm / s to 1100 mm / s. The laser output P is reduced from 370 W to 300 W, but this is because the experiment was conducted based on a map created using the laser output P and scanning speed v as conditions, and was not intentionally reduced. In this embodiment, the fabrication conditions in the second area 62 and the non-generation area 65 are the same.

[0033] Figure 8 is a magnified cross-sectional photograph showing a portion of the structure W2 fabricated after the condition adjustments shown in Figure 7. Figure 9 is a diagram showing the correspondence between energy density E and fabrication conditions, and shows data when the energy density E is reduced by decreasing the laser output P, ​​which is used as the adjustment condition. In the example shown in Figure 9, the laser output P is changed from 370W to 136W. Figure 10 is a magnified cross-sectional photograph showing a portion of the structure W3 fabricated after the condition adjustments shown in Figure 9.

[0034] Structures W1, W2, and W3 are all modeled after water pipes of similar shape, but their finished shapes differ because they were fabricated under different conditions using the metal additive manufacturing apparatus 1.

[0035] As shown in Figure 8, when the scanning speed v was increased during fabrication, almost no deformation occurred at the top surface 66, and it was possible to reduce the shape error to 0.5 mm or less. On the other hand, as shown in Figure 10, when the laser output P was decreased during fabrication, although some improvement in shape error was obtained, multiple voids 67 occurred due to a decrease in relative density, resulting in a decrease in quality. The occurrence of multiple voids 67 leads to the disadvantage that the product is prone to cracking due to mechanical stress when water pressure acts on the inner circumference of the structure W3 during use.

[0036] As described above, in order to adequately melt the metal powder M in order to ensure a quality such that no voids 67 are formed, the laser output P needs to be of a certain magnitude. Therefore, when adjusting to reduce the energy density E, it is preferable to use conditions other than the laser output P. Specifically, this can be adjusted by increasing the value of any of the scanning speed v, scanning pitch s, or layer thickness t as the molding conditions in the generation unit 64.

[0037] (1) In the metal additive manufacturing apparatus 1 of the first embodiment described above, when manufacturing the generation part 64 of the first area part 61, where the manufacturing parts W11, W12, and W13 are not directly below and there is no support underneath, the scanning speed v is increased to reduce the energy density E so that it is the same as the laser output P when manufacturing the non-generation part 65 and is about the same as the irradiation temperature of the non-generation part 65. This makes it possible to suppress the occurrence of warping in the layer that causes shape deformation in the first area part 61 and to improve shape accuracy.

[0038] (2) Furthermore, when adjusting to reduce the energy density E, the laser output P can be maintained without reducing its magnitude, so that a quality such that no voids 67 are formed in the finished structure W2 can be ensured.

[0039] (3) Figure 11 is a diagram illustrating the occurrence of shape errors when the radius R of the conduit 60 is changed during manufacturing using a comparative configuration of the metal additive manufacturing apparatus 1 that does not have a condition adjustment unit 52. Figure 12 is a diagram illustrating the occurrence of shape errors when the radius R of the conduit 60 is changed during manufacturing using the metal additive manufacturing apparatus 1 of the first embodiment. As shown in Figure 11, when the first area 61 and the second area 62 are irradiated and manufactured under the same conditions without the condition adjustment unit 52, the shape error was kept to 0.5 mm or less when the radius R was 2 mm or less. On the other hand, as shown in Figure 12, in manufacturing using the metal additive manufacturing apparatus 1 of the first embodiment, the shape error was kept to 0.5 mm or less in the range of radius R up to 8 mm.

[0040] In other words, even large pipe members with a radius R of about 8 mm can be fabricated while maintaining shape accuracy. As a result, the number of water pipe shapes that can be fabricated by the metal additive manufacturing apparatus 1 increases, which in turn reduces the manufacturing time and lifespan of the structure W2 compared to manufacturing by other methods such as forging or welding, including manual work, and ultimately reduces manufacturing costs.

[0041] (4) In the metal additive manufacturing apparatus 1 of the first embodiment described above, a copper alloy is used as the metal powder M. Copper alloy powder has a high reflectivity, so it does not easily absorb the energy of the laser light, and the temperature of the powder does not rise easily. Furthermore, even if the temperature of the powder rises and exceeds the melting point, its thermal conductivity is about twice that of aluminum and 20 times that of stainless steel, so it cools down quickly and solidifies below the melting point. For this reason, the time during which the powder is flowing above the melting point during laser irradiation is very short, making it difficult to obtain high-density layered metal. In other words, copper alloys are susceptible to the effects of excessive heat input during laser irradiation, but according to the first embodiment described above, it is possible to manufacture with high quality and accuracy even with copper alloys, as described above.

[0042] B. Other embodiments: (B1) In the metal additive manufacturing apparatus 1 of the first embodiment described above, the generation area 64 and the non-generation area 65 within the same layer are distinguished, and the scanning speed v is greatly changed for the generation area 64. However, the scanning speed v may be adjusted for each layer. For example, in the above example, the energy density E may be reduced for the entire 399 layer having the generation area 64.

[0043] Note that while the layer thickness t cannot be adjusted differently within a single layer, the overall thickness of a single layer can be adjusted by adjusting the amount the lifting table 22 of the object support device 20 lowers. The scanning speed v and scanning pitch s may be adjusted for each layer as described above, or they may be adjusted only for the generation unit 64 according to the scanning area within a single layer.

[0044] (B2) In the metal additive manufacturing apparatus 1 of the first embodiment described above, a water tube, which is a coil for high-frequency heat treatment, was used as an example of a structure W, but the structure W is not limited to such a water tube. Any structure W having a first area 61 in which the solidified fabricated part is not located at the bottom in the layering direction Z, and a second area 62 in which the fabricated part is located at the bottom, can be fabricated using the metal additive manufacturing apparatus 1 according to this disclosure.

[0045] (B3) In the metal additive manufacturing apparatus 1 of the first embodiment described above, the scanning speed v was adjusted to be large when manufacturing the generation section 64. However, when manufacturing the entire first area section 61, including the non-generation section 65, the heat input may be adjusted to be lower than that of the second area section 62, with a lower energy density E.

[0046] (B4) In the metal additive manufacturing apparatus 1 of the first embodiment described above, the energy density E was adjusted by increasing the scanning speed v, but it may also be adjusted by increasing parameters such as the scanning pitch s and the layer thickness t. Alternatively, multiple of these parameters may be combined for adjustment.

[0047] (B5) In the metal additive manufacturing apparatus 1 of the first embodiment described above, identification information for identifying the warping area 64 was identified based on data from prior tests in which warping actually occurred. Alternatively, the warping area may be identified by estimation based on the relationship between the radius and tangent angle of the conduit where warping is predicted to occur, or the length of the area where the metal powder M has not solidified directly below the irradiation area, based on accumulated data during manufacturing.

[0048] This disclosure is not limited to the embodiments described above, and can be implemented in various configurations without departing from its spirit. For example, the technical features in each embodiment corresponding to the technical features in each form described in the summary of the invention can be replaced or combined as appropriate in order to solve some or all of the above-mentioned problems, or to achieve some or all of the above-mentioned effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate. [Explanation of symbols]

[0049] 1...Metal additive manufacturing apparatus, 10...Chamber, 11...Metal additive manufacturing apparatus, 20...Modeling support device, 21...Modeling container, 22...Lifting table, 23...Base, 30...Powder supply device, 31...Powder storage container, 32...Supply table, 33...Recoater, 40...Beam irradiation device, 50...Control device, 51...Memory unit, 52...Condition adjustment unit, 60...Pipeline, 61...First area unit, 62...Second area unit, 64...Generating unit, 65...Non-generating unit, 66...Top surface unit, 67...Vacuum, W, W1, W2, W3...Structure, W11, W12, W13...Modeling unit

Claims

1. A metal additive manufacturing apparatus that repeatedly irradiates a powder layer, which is a layer of metal powder, with a light beam to melt and solidify it, thereby creating a layered structure. The structure has a first area where the fabricated portion solidified by the light beam is not located at the bottom in the stacking direction, and a second area where the fabricated portion is located at the bottom. A storage unit that stores identification information for distinguishing the first area and the second area in advance, Based on the aforementioned identification information, a condition adjustment unit adjusts the molding conditions that determine the energy density so that when molding the first area, heat is input at a lower energy density than when molding the second area. Equipped with, The aforementioned storage unit is The identification information further stores information that identifies a portion of the first area where warping exceeding a predetermined shape error occurs when fabricated with the same energy density as the second area, and a portion where warping does not occur when fabricated with the same energy density as the second area. The aforementioned condition adjustment unit is The beam output, which is the output of the light beam, is the same as the beam output during fabrication of the non-generation part, and the beam irradiation temperature in the generation part is the same as the beam irradiation temperature in the non-generation part. During the fabrication of the aforementioned generating unit, conditions different from the beam output are adjusted as the fabrication conditions. Metal additive manufacturing equipment.

2. The metal additive manufacturing apparatus according to claim 1, wherein the metal powder is a copper alloy.

3. The aforementioned structure has a pipeline through which fluid flows, The metal additive manufacturing apparatus according to claim 1 or 2, wherein the first area is formed on the inner circumference of the curved surface that forms the pipeline.

4. The metal additive manufacturing apparatus according to claim 3, wherein the structure is a coil for high-frequency heat treatment.

5. The aforementioned condition adjustment unit is The metal additive manufacturing apparatus according to any one of claims 1 to 4, wherein the manufacturing conditions include adjusting at least one of the following: the scanning speed of the light beam, the scanning pitch of the light beam, and the layer thickness of the powder layer.

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